Polyester fibers having improved hydrophilicity as a result of modification with phosphoric acid,phosphorous acid or perchloric acid



United States Patent O 3,460,896 POLYESTER FIBERS HAVING IMPROVED HYDRO-PHKLICITY AS A RESULT OF MODIFICATION WITH PHOSPHORIC ACID, PHOSPHOROUSACID R PERCHLORIC ACID John R. Caldwell, Kingsport, Tenn., assignor toEastman Kodak Company, Rochester, N.Y., a corporation of New Jersey NoDrawing. Filed Oct. 14, 1964, Ser. No. 403,907 Int. Cl. D06p 3/52, 3/00U.S. Cl. 8-1155 4 Claims As is well known, various polymeric materialssuch as high molecular weight linear polyesters which are generallyuseful in the production of products such as fibers, filaments, yarns,fabrics, and the like have certain draw- 3,460,896 Patented Aug. 712,1969 insoluble particles are formed in the product mass'which tend toclog the minute orifices of spinnerettes when the filaments are producedby the melt spinning process.

'In addition to the above mentioned expedients, Canadian Patent No.620,001 describes a process for treating polyester fibers in which anorganic acid is applied and ice : the treated fiber is then heated at atemperature of 2.00

to 220. All of the acids disclosed in this patent contain organicradicals and hence are not inorganic acids nor do they or can theyproduce the effects on polyester fiber materials which are produced byinorganic acids in accordance with the present invention to be setforthhereinafter. A somewhat related disclosure is that of US. 2,893,896which describes the treatment of ,polyester sub strates with halogenatedfatty acids but makes-no men tion of the application of inorganic acidsas employed in the present invention. In another disclosure, namely, Ca-

backs 0r deficiencies whichlimit their usefulness in such products. Forexample, it is known that many types of polymeric materials whenextruded in the form of filaments and converted into yarns do not" havethe desired resistance to soiling by a variety of substances, especiallyoily or greasy-substances, which'such yarn materials .2

of fibers and filaments for textile uses. As to wettability,

this is an especially important property when such polyester fibers areemployed in apparelfabrics because the transmission of moisture from theskin is facilitated if the fiber material employed has good wettability.Such readily wettable fibers possess the property of wicking away waterfrom the body for more efficient evaporation and thus greater comfort tothe wearer. In other applications such as the sizing'of fibers andyarns, wettability is an important property in the application ofvarious coatings such as gelatin, polyvinyl alcohol and other substanceswhich are normally deposited from aqueous or alcohol or other solutions.It is also apparent that 'dyeability is an important property inpolyester textile fibers in order to obtain uniform and permanentcoloration of the fiber material by the dyes generally employed for thispurpose as well as to enable the material to receive and permanentlyretain printing inksand other coloring materials.

Various expedients have been employed in the prior art to overcome theabove mentioned drawbacks and deficiencies inherent in the use of linearpolyesters for the manufacturers of fibers and filaments. Among thesemay be mentioned the application of various sizing or coatingcompositions which form an adherent surface layer which tends to providethe desired properties in the finished material. Another is theemployment in the reaction mixture from which the polyester is formed ofa substance which will react chemically with the polyester to add onchemical groups which will provide the desired properties. In this caseit has been found that under certain circumstances unstable productsresult and in some "cases undesirable nadian 652,277, which is anextension of the invention described in Canadian 620,001, there isdescribed the application-to polyester fibers of salts of organic acidstogether with'a volatile base. This patent, like 620,001, does notdisclose any salts of inorganic acids such as are used in the instantinvention as will be avident from the detailed descriptionwhich-follows. U.S. 2,805,173 discloses'jthe treatment of 'a-polyseterfilm base, not 'a fiber, with chlorosulfonic aciddissolved intrichloroethylene or other organic solvent. Chlorosul: fonic acid is anacid chloride which decomposes in water. Hence, it cannot be applied toa fiber material from aqueous solutions. This disclosure is therefore inno way pertinent to the present specific invention.

It is thus apparent from the above discussion that it was in no wayrecognized or suggested inthe prior art that the valuable fiberproperties described in the present application could be obtained bytreating polyester fibers with inorganic acids under the mild conditionsemployed in the instant invention.

' The present invention has as an object to provide polyester fibershaving improved surface characteristics which give the fiber materialgood wettability, excellent adhesive properties with respectto-deposited coatings, dyes and printing iriks and especially goodresistance to soiling, particularly by oily soils.

Another object is to provide a convenient and readily applied andcontrolled process for the treatment of polyester fibers, whether in theform of cut staple, spun yarn, continuous filaments or continuousfilament tow, yarns or knitted or woven fabrics and whether used aloneor in admixture or associated with another synthetic fiber material orwith natural fibers, whereby the polyester material is given a specialsurface which gives it the properties referred to in the precedingparagraph;

Other objects will appear hereinafter.

These objects are accomplished by the following invention whichcomprises applying from aqueous solution to polyester fiberseither aloneor in association with other synthetic or natural fibers and in the formof fibers as such, or in the form of spun yarn, continuous filaments orcontinuous filaments tow, or fabrics an inorganic acid having adissociation constant of at least 10- such as phosphoric acid,phosphorous acid, perchloric acid and sulfuric acid, or a salt ofsuchacids with ammonia or volatile amines in an amount corresponding to from0.1 percent to 5.0 percent and preferably from 0.3 percent to 1.0percent based on the weight of the polyester material, heating the sotreated polyester material to a temperature within the range of 200 C.for a period of 0.1 to 30 minutes'and thereafter removing the acid bywashing with water. Surprisingly, it was found that this relatively mildtreatment with inorganic acids produces a profound change in the surfaceof the polyester fiber material, convetting it from a highly hydrophobicsurface which has poor wettability, poor adhesion with respect todeposited coatings, especially those deposited from aqueous media, andpoor resistance to soiling, to a material which has, not only excellentwettability and adhesion properties but also excellent resistance tosoiling, particularly by oily soils.

Although reference has been made above to the use as a treating agentfor the polyester fiber material of a single acid or salt, in accordancewith the invention a mixture of such acids or salts may be employed andapplied in the range of concentrations stated.

It will be seen from the above that the present process is essentially athree step process, namely, (1) treating the fiber surface with anaqueous solution of an inorganic acid or a salt thereof, (2) heating thetreated fiber to a mild temperature for a brief period and (3)thereafter removing the acid or salt solution from the fiber. While itis not known exactly what type of chemical transformation takes place inthe superficial surface layers of the polyester fibers and no specifictheory is relied upon for an explanation, it is to be assumed that somesort of hydrolytic transformation or rearrangement of the polyestermaterial takes place whereby polar groups (presumably both hydroxyl andcarboxyl) are formed thereon, thus changing the polyester surface, whichis normally extremely hydrophobic and repellent to aqueous media, to onewhich is readily wettable by water or aqueous solutions or suspensionsof various substances such as gelatin, polyvinyl alcohol, dyes, printinginks and other materials. Such polar groups remain permanently attachedto the fiber material during conditions of use. Another surprising andunexpected result of the treatment of the polyester fiber material byinorganic acids or their salts in accordance with the invention is thatthe material is thereby rendered highly resistant to soiling,particularly by oily soils of various kinds.

One phase of the present process which should be emphasized is the factthat no chemical groups or layers of another material are added to thesurface of the polyester material during treatment and the acid (orsalt) merely acts to effect some sort of hydrolytic chemicaltransformation of the superficial surface layers under the influence ofmild heat but is subsequently removed as such and does not remain in thefinished product. This, among others, is one of the features of thepresent invention which sets it off from and distinguishes it from theprior art as discussed above. Another distinguishing feature is the factthat inorganic acids are employed to effect the hydrolytictransformation and they are permitted to remain on the fiber materialunder the influence of mild heating for a sufiicient length of time toproduce the desired effect.

As indicated above and in the examples to follow, the polyester fibermaterial can be treated while in any desired physical form as, forexample, cut staple, spun yarn, single filaments, continuous filamenttow, as such, either alone or in blends with other man made fibers orfilaments such as cellulose acetate, viscose rayon, nylon and the likeor with various kinds of natural fibers such as cotton, wool and others,or in the form of knitted, Woven or other types of fabrics. For example,a fabric made from 60 percent polyester fiber and 40 percent cotton canbe treated as described above and in accordance with the procedureillustrated in the examples forming a part of this specification. In asimilar fashion, the process may be applied to a blend of 50 percentpolyester fibers and 50 percent wool or viscose.

Reference has been made to applying to the polyester fiber material anaqueous solution of the inorganic acid or a salt thereof so as to applyto the polyester material from 0.5 to 5.0 percent and preferably 0.3 to1.0 percent of the acid or salt, based on the weight of the polyester.In some cases the solvent media may be a mixture of water with anorganic solvent having afiinity for or a solvating action on thepolyester material such as a lower alcohol. The concentration of theacid or salt in such media will be determined by the amount of the saltor acid desired to be deposited within the weight percentage limits justindicated. When the acid is applied from aqueous solutions surfactantsmay be used to facilitate uniform wetting of the hydrophobic polyestersurface. The surfactants may be of the anionic, cationic or nonionictypes. Examples of typical surfactants falling in these categories aresodium dodecyl sulfate, octadecyl amine The acid or salt solutions maybe applied by either continuous or bath operations using conventionaldip, spray, roll or other suitable equipment known to those skilled inthe art to which the invention relates.

Reference has also been made to that step of the process of theinvention in which, after application of the acid or salt treatingsolution, the treated polyester fiber material is heated underconditions that evaporate substantially all of the solvent as, forexample, Within a temperature of -200" C. and preferably -160 C. for aperiod of 0.1 to 30 minutes. The time and temperature required willdepend upon a number of variables such as the physical form and chemicalcomposition of the polyester, the specific acid used, the amount of acidto be deposited and the like. In a typical case, a fabric is passedthrough a 0.2 percent solution of phosphoric acid, then into a hot airoven having a temperature of C. The water is evaporated Within a fewseconds by a hot air blast and the polyester fiber material in eitherfiber, continuous filaments, tow, or fabric form is then subjected tothe same temperature for one minute or more as may be required.

Fibers treated by the process have improved adhesion for coatings ofgelatin, rubber, various vinyl polymers such as polyvinyl butyral andmany others. As indicated above, a particularly valuable aspect of theprocess of the invention is the treatment of polyester fibers in any ofthe forms mentioned above to improve their resistance to soiling. Thediscoloration in fabrics may be caused, for example, by the absorptionof oily materials in perspiration or by contact with lubricating oils,foods, etc. It also has been demonstrated that polyester fibers have atendency to pick up oils and greasy materials from drycleaning fiuidsand laundry water in which other oil soiled fabrics have been treated.It has been found, quite surprisingly, that the hydrophilic surfaceproduced by the process of the invention enables the treated polyesterfiber material to resist Wetting by oils and greasy materials and toretain their original white color under severe conditions of use.

The polyesters which are susceptible to improvement in accordance withthe objects of the invention as stated above, are those commonlyemployed for the manufacture of textile fibers. Thus, the polyesterstreated in accordance with this invention can be most advantageouslyderived from terephthalic acid, 4,4-sulfonyldibenzoic acid,4,4'-diphenic acid, 1,2-di(p-carboxyphenyl)-ethane,l,2-di(p-carboxyphenoxy)-ethane, 4,4-dicarboxy-diphenyl ether, and thevarious esters of these acids such as the lower alkyl diesters. Thesecompounds can be generically grouped as hexacarbocyclic nucleardicarboxylic bifunctional compounds wherein the carboxyl radicals arenuclearly situated in a para relationship. Such compounds can be reactedin accordance with the well-known techniques illustrated in numerousissued patents with bifunctional glycols containing from about 2 toabout 10 carbon atoms. Examples of such glycols include ethylene glycol,tetramethylene glycol, 2,2,4,4-tetraalkyl-1,3-cyclobutanediol,pentamethylene glycol, neopentylene glycol, 1,4 cyclohexanedimethanol,quinitol, 1,4 bis(hydroxyethyl)benzene, etc. Illustrative of the moreadvantageous polyesters are poly(ethylene terephthalate), the polyesterfrom pentamethylene glycol and 4,4-sulfonyldibenzoic acid, the polyesterfrom 1,4-cyclohexanedimethanol and terephthalic acid and variousmodified polyesters related thereto, e.g., those wherein up to 30 molepercent of another aromatic dicarboxylic acid or an aliphaticdicarboxylic acid is employed as a modifier.

The test for soiling and to determine the improved resistance to soilingof fibers treated in accordance with our invention is as follows:

SOILING PROCEDURE A soiling solution was prepared by the followingcomposition:

The lard and stearic acid were melted together in a beaker and themineral oil, premixed with the carbon black, was added and stirred intothe melt and the carbon tetrachloride then added to form the solution. 2/2 by 2 /2" swatches of a bleached cotton print cloth (such as standardbleached cotton print supplied commercially for this purpose) wereimmersed in the soiling solution contained in a screw-cap bottleequipped with means for continuous shaking or agitation. Agitation ofthe swatches in the soiling solution was continued for two minutes. Thesamples were then taken from the bottle and dried in air at roomtemperature.

SOIL TEST PROCEDURE The antisoiling properties of polyester fiberstreated in accordance with the present invention was determined bywashing a clean swatch of a fabric woven from such fibers together withtwo swatches of cotton fabric which had been presoiled by treatment withthe soiling solution described above. A clean 2 /2 x 2 /2" swatch of thepolyester fabric was immersed, together with the two soiled cottonswatches, in 100 cc. of a wash solution made up by dissolving 2 grams ofa detergent sold under the trade mark Tide in 1000 cc. of demineralizedwater contained in a l-pint Launder-Ometer jar provided with suitableheating means. Fifteen stainless steel balls were added, the jar closedby its glass cap and rotated at about 30 r.p.m. for 30 minutes at 160 F.This constitutes one soiling cycle. The swatches were then removed fromthe jar and the polyester swatch washed with demineralized water anddried in a forced air oven at 250 F. Swatches of untreated polyesterfabrics, when washed with soiled cotton swatches in this manner, pickedup soil therefrom and came out of the wash solution colored gray to darkgray. However, the same fabrics, but treated in accordance with theinstant invention, picked up little, if any, color when washed severalseparate and consecutive times with fresh pieces of the soiled cottonfabric.

In the following examples and description I have set forth several ofthe preferred embodiments of my invention but they are included merelyfor purposes of illustration and not as a limitation thereof.

Example I A solution of 4 g. H PO and 0.5 g. Pluronic L-44 was preparedin 200 cc. of water. Pluronic L-44 is a nonionic polyalkylene oxidewetting agent made by Wyandotte Company.

A fabric made from poly(ethylene terephthalate) fibers was soaked in thesolution, pressed to twice its original weight, and heated at 150 C. for5 minutes. A fabric made from poly(1,4-cyclohexanedimethyleneterephthalate) was treated in a similar way. After washing and drying,the fabrics had greatly improved resistance to soiling when subjected tothe above described soiling test.

Example H An add-on of 0.3 percent phosphorus acid was applied fromaqueous solution to a fabric made from poly(ethyl ene terephthalate).The water was evaporated and the fabric was heated at 120 for 5 minutes.After washing, the fabric had excellent resistance to soiling. Similarresults were obtained on fabrics made frompoly(1,4-cyclohexanedimethylene terephthalate), poly(ethylene 2,6-naphthalenedicarboxylate) and poly(pentamethylene 4,4-sulfonyldibenzoate Example III An add-on of 0.4 percent phosphoric acidwas used, as described in Example II. The treated fabrics had excellentresistance to soiling.

Example IV An add-on of 0.3 percent phosphoric acid and 0.2 percentsulfuric acid was used as described in Example II, with similar results.

Example V An add-on of 0.1 percent sulfuric acid was applied fromaqueous solution to a fabric made from poly(ethylene terephthalate). Thewater was evaporated at -100 7 with a hot air blast and the fabric wasthen subjected to a temperature of approximately for 1.0-1.5 minutes.Alternatively, a temperature of and reaction time of 20-30 seconds canbe used. The fabric was then passed through a water bath to remove theresidual acid. The treated fabric had improved adhesion for rubber latexcoatings. It had greatly improved resistance toward soiling by oilysoils when tested as above described.

For comparison, a fabric was treated with an add-on of 0.1 percenthydrochloric acid and then subjected to the same heating conditions asdescribed above. It did not show any improvement with respect to soilresistance or adhesion of latex coatings.

Example VI A tow of poly(ethylene terephthalate) fibers was passedthrough a bath to give an add-on of 0.6 percent phosphoric acid, basedon the fiber weight. Butyl alcohol or isopropylalcohol-water was used asthe solvent for the phosphoric acid. The bath also contained 0.1 percentnonionic wetting agent to give uniform wetting of the fibers. The towwas then passed through a hot air blast at 100-110 to evaporate most ofthe water. The tow was then run through a crimper at a temperature of-150". The fibers had excellent resistance to soiling 'by oily soils.

Example VII Fibers of poly (ethylene terephthalate) were passed througha bath to give an add-on of 0.4 percent perchloric acid, based on thefiber weight. After the water was evaporated, the fibers were heated at80-90 for 20 minutes. They had improved resistance to soiling by oilysoil.

An amine salt of perchloric acid can be used such as the pyridine,ethylamine or trimethylamine salt. When a salt is used, it may beadvantageous to employ a higher reaction temperature such as 120-140.

Example VIII A fabric made from poly(ethylene terephthalate) was paddedwith a water solution of the monopyridine salt of sulfuric acid, to givean add-on of 0.5 percent. The water was evaporated at 100 and the fabricwas then heated at 120130 for one minute. The fabric was washed in waterto remove the acid. The treated fabric had improved resistance tosoiling.

Example IX A fabric made from poly(etl1ylene terephthalate) was boiledfor 5 minutes in a 2 percent solution of sodium hydroxide. Although someloss in weight occurred, the fabric did not show any improvement in soilresistance.

The same type of fabric was padded with 1.0 percent sodium hydroxidefrom water solution. The water was evaporated and the fabric was heatedat 120 for minutes. After washing in water, the fabric did not show anyimprovement in soil resistance.

It is thus apparent that the treatment of polyester fibers with thestrong inorganic acids of the present invention produces a result thatis entirely different and unpredictable from the results obtained bytreatment with alkalies.

Example X A fabric made from poly(ethylene terephthalate) was boiled forperiods of 1 minute to 30 minutes in a 10 percent aqueous solution ofphosphoric acid. None of the fabrics showed any improvement with respectto adhesion of coatings or resistance to soiling. It is believed thatany hydrolysis products formed under these conditions are dissolved awayfrom the fiber surface during the reaction. Hence, there is no change inthe surface properties of the fiber.

In contrast, when the acid treatment is carried out under the specialconditions disclosed in the present invention, an entirely difierenttype of reaction takes place. Polar groups, probably carboxyl andhydroxyl, are generated by hydrolytic cleavage of polymer chains. Thesegroups remain attached to the polymer surface, thereby imparting new andvaluable properties. This is an entirely unpredictable discovery.

It will be seen from the above description of my invention that a meansis thereby provided for bringing about a profound change in a normallyhydrophobic, difiicultly wettable polyester fiber material which rendersthe surface of the material hydrophilic and readily wetta- =ble. Inaddition the invention completely changes the soiling characteristics ofthe polyester fiber material, from one which is readily soilable,particularly by oily soils in laundering with other fibers or fabricswhich have been soiled by such materials, to a material which is highlyresistant to soiling of various kinds including such oily soils. It isto be particularly noted that quite unexpectedly the polyester fibermaterial is given excellent wattability, good adhesive properties withrespect to deposited layers such as gelatin, poly(vinyl alcohol), dyes,printing inks and the like and high soiling resistance characteristicsby an extremely simple procedure which does not involve the addition ofany material to the poly ester itself, as by the deposition of coatingsor the addition of any chemical groups thereto. As will be obvious fromthe above description the acid or salt applied to the polyester fibermaterial remains on it, in accordance with the invention, only longenough to accomplish the development of the permanently attached polargroups in the polyester surface but is subsequently completely removedand does not remain in the treated fiber. Thus it can be said that anentirely unexpected and highly valuable improvement in the treatment ofpolyester fibers results from the present invention.

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof,variations and modifications can be effected within the spirit and scopeof the invention as described hereinabove, and as defined in theappended claims.

I claim:

1. A high melting crystalline linear polyester fiber material made bythe process which comprises (1) coating said fibers with an essentiallyaqueous solution containing an inorganic acid having a dissociatingconstant of at least 10*, of ammonium salts of such acids, or volatileamine salts of such acids, wherein said inorganic acid is phosphoricacid, phosphorous acid, or perchloric acid, (2) heating said coatedfibers to form substantially dry acid coated fibers having on thesurface from about 0.05 to about 5% by weight of said acid, (3) heatingat to 200 C. said substantially dry acid coated fibers to form polargroups on the fiber surfaces without significant alternation of thephysical surface structure, and (4) washing said fibers to removesubstantially all of said acid.

2. A high melting, crystalline linear polyester fiber material asdefined by claim 1 produced by the use of phosphoric acid.

3. A high melting, crystalline linear poleyster fiber material asdefined by claim 1 produced by the use of phosphorous acid.

4. A high melting, crystalline linear polyester fiber material asdefined by claim 1 produced by the use of perchloric acid.

References Cited UNITED STATES PATENTS 3,107,968 10/1963 Pascal 8-55FOREIGN PATENTS 683,218 11/ 1952 Great Britain. 749,456 5/1956 GreatBritain.

NORMAN G. TORCHIN, Primary Examiner J. CANNON, Assistant Examiner US.Cl. X.R. 855

1. A HIGH MELTING CRYSTALLINE LINEAR POLYESTER FIBER MATERIAL MADE BYTHE PROCESS WHICH COMPRISES (1) COATING SAID FIBERS WITH AN ESSENTIALLYAQUEOUS SOLUTION CONTAINING AN INORGANIC ACID HAVING A DISSOCIATINGCONSTANT OF AT LEAST 10**-3, OF AMMONIUM SALTS OF SUCH ACIDS, ORVOLATILE AMINE SALTS OF SUCH ACIDS, WHEREIN SAID INORGANIC ACID ISPHOSPHORIC ACID, PHOSPHOROUS ACID, OR PERCHLORIC ACID, (2) HEATING SAIDCOATED FIBERS TO FORM SUBSTANTIALLY DRY ACID COATED FIBERS HAVING ON THESURFACE FROM ABOUT 0.05 TO ABOUT 5% BY WEIGHT OF SAID ACID, (3) HEATINGAT 80 TO 200*C. SAID SUBSTANTIALLY DRY ACID COATED FIBERS TO FORM POLARGROUPS ON THE FIBER SURFACES WITHOUT SIGNIFICANT ALTERNATION OF THEPHYSICAL SURFACE STRUCTURE, AND (4) WASHING SAID FIBERS TO REMOVESUBSTANTIALLY ALL OF SAID ACID.